Color composition for color filter, color filter using the composition and liquid crystal display device

ABSTRACT

A color filter and a liquid crystal display device with the color filter that includes a substrate; and a color layer formed on the substrate and constituting color pixels of a plurality of colors, wherein the color layer is formed through a curing of a color composition comprising at least acrylic resin and a coloring agent, wherein the acrylic resin contains a copolymer formed of a first vinyl monomer having a benzyl group and a second vinyl monomer having a carboxyl group, the first vinyl monomer having a function of regulating a retardation of a color layer, the copolymer having a weight average molecular weight of 3000 to 11000 and an acid value of solid matter falling within the range of 30 to 85.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/662,972, filed May 13, 2010, pending, which claims priority based onprior Japanese Patent Application No. 2009-118643 filed May 15, 2009,all of the disclosures of which are incorporated herein by reference.

BACKGROUND

1. Field

This invention relates to a color composition for a color filter, to acolor filter where this color composition is employed, and to a liquidcrystal display device which is provided with this color filter.

2. Description of the Related Art

In recent years, thin display devices such as a liquid crystal displaydevice are increasingly demanded to enhance the picture image andpower-saving thereof and to lower the manufacturing cost thereof.Therefore, in the case of the color filter to be employed in suchdisplay devices, it is desired to employ a photosensitive colorcomposition which is sufficiently high in color purity, in brightnessand in contrast and makes it possible to produce a fine patternaccurately and at a low cost while developing the double refraction inconformity with various kinds of liquid crystal display modes.

Especially, with respect to the viewing angle characteristics of liquidcrystal display device, it is now demanded to exhibit a very high levelof display quality. More specifically, on displaying black color ofliquid crystal (in the case of normally black display, the black colorin field-off state), it is demanded to realize pure black color and todisplay this pure black color at a wide viewing angle. For this purpose,various ideas have been practiced attaching importance to the featuresof a retardation film, to the method of aligning the liquid crystalmolecules and to the method of driving the liquid crystal molecules.Since the display of “black” to be dealt therewith is directly relatedwith the value of contrast ratio on the occasion of ON/OFF of drivingsignals, the display thereof is important in this respect.

Further, there is such a high level of demand for the “black display”that even if there is a minute retardation (a retardation in thicknessdirection) which is caused to generate by each of color pixelsconstituting a color filter to be formed through the dispersion oforganic pigments, it is demanded to make sure that the black display canbe prevented from being badly influenced. In order to meet this demand,various methods have been tried to reduce the quantity of retardationthat the color filter may exhibit, the methods including one wherein amacromolecule having a planar structural group on its side chain isintroduced into a color layer constituting a color pixel, or one whereina double refractive index-reducing particles having a double refractionwhich is opposite in sign to that of a macromolecule is introduced intoa color layer constituting a color pixel (see for example, JP-A2000-136253 and JP-A 2000-187114).

Further, there has been proposed an idea to incorporate aretardation-adjusting agent in the color layers of color filter, thusenabling each of subpixels to have a different retardation, therebymaking it possible to enable the viewing angle compensation of blackstate of a liquid crystal display device to be effected in thewavelength of almost all visible light zone without necessitating theprovision of a polymeric liquid crystal layer in addition to the colorlayers or without necessitating the change of thickness in each ofsubpixels (see for example, JP-A 2008-20905 and JP-A 2008-40486).

However, in the cases of the prior art wherein the double refractiveindex-reducing particles or the retardation-adjusting agent is employed,even if it is possible to adjust the retardation of a color polymer filmformed a coated film, it has been found impossible to optimize thecharacteristics of color resist employed as a starting material forforming color pixels. Specifically, it has been found difficult toconcurrently optimize not only the developing properties of a colorresist at the step of photolithography, the adhesion of the color resistto a substrate and the storage stability of the color resist but alsothe adjustment of retardation.

Incidentally, it has been found out by the present inventors that thevalue of retardation in thickness direction which the color layer mayexhibit greatly differs depending on the kinds of pigment to be employedand that the magnitude of the value of retardation in thicknessdirection becomes larger depending on the pulverization or dispersion ofthe pigment or on the kinds of matrix resin (for example, acrylic resin,cardo resin, etc.).

For these reasons, in the case of the conventional methods where doublerefractive index-reducing particles or the conventionalretardation-adjusting agent is employed, even if it is possible toincrease the value of retardation in thickness direction in the positivedirection, it is difficult to shift the retardation of color layerexisting in a plus region toward less than +2 nm or in the negativedirection which is required for obtaining “black” of a higher level.

Meanwhile, with respect to the demand for contrast, although there hasbeen proposed an idea of using acrylic resin comprising, as essentialcomponents, benzyl (metha)acrylate and (metha)acrylic acid (see forexample, JP-A 10-20485), it is still impossible to realize thedevelopment of double refraction in conformity with each of variousliquid crystal display modes.

SUMMARY

It is objects of the present invention to provide a color compositionfor a color filter, which is not only excellent in long-term storagestability, heat resistance and developing speed, but also suited forforming the color filter which is excellent in adhesion to a substrate,hardness, solvent resistance and alkali resistance, to provide a colorfilter which can be formed by making use of this color composition for acolor filter and exhibits a value of retardation in thickness direction(Rth) which is necessary for obtaining a high level of black color inthe off state display, and to provide a liquid crystal display devicewhich is provided with this color filter and capable of greatlyimproving oblique visibility.

According to a first aspect of the present invention, there is provideda color composition for a color filter, which comprises at least acrylicresin and a coloring agent, wherein the acrylic resin contains acopolymer formed of a first vinyl monomer having a benzyl group and asecond vinyl monomer having a carboxyl group, the first vinyl monomerhaving a function of regulating a retardation of a color layer obtainedby curing of the color composition, the copolymer having a weightaverage molecular weight of 3000 to 11000, and an acid value of solidmatter of the copolymer being confined to 30 to 85.

According to a second aspect of the present invention, there is provideda color filter which comprises: a substrate; and a color layer formed onthe substrate and constituting color pixels of a plurality of colors,wherein the color layer is formed through a curing of a colorcomposition comprising at least acrylic resin and a coloring agent,wherein the acrylic resin contains a copolymer formed of a first vinylmonomer having a benzyl group and a second vinyl monomer having acarboxyl group, the first vinyl monomer having a function of regulatinga retardation of a color layer, the copolymer having a weight averagemolecular weight of 3000 to 11000 and an acid value of solid matterfalling within the range of 30 to 85.

According to a third aspect of the present invention, there is provideda liquid crystal display device which is provided with the color filterof the second aspect of the present invention.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a cross-sectional view schematically illustrating the colorfilter according to one embodiment of the present invention; and

FIG. 2 is a cross-sectional view schematically illustrating one exampleof a liquid crystal display device which is provided with a color filterof the present invention.

DESCRIPTION OF EMBODIMENTS

Next, various embodiments of the present invention will be explained.

As a result of intensive studies made by the present inventors on thecolor composition for forming the color pixels of color filter, thefollowing facts have been found out.

(1) A color composition containing a copolymer formed throughcopolymerization of a first vinyl monomer having benzyl group and asecond vinyl monomer having carboxyl group is excellent in long-termstorage stability and developing speed, and a color layer obtained bythe curing of the color composition through the light exposure and/orbaking thereof is enabled to give a value of retardation in thicknessdirection (Rth) ranging from +1 nm to −10 nm and is excellent in heatresistance, in adhesion to a substrate, in hardness, in solventresistance and in alkali resistance.

(2) When color pixels are formed by means of a color filter-formingmethod using an alkali-soluble type photosensitive compositioncontaining the aforementioned color composition, it is possible to forma pattern of color pixels at an optimum developing speed and with highaccuracy.

The present invention is based on these findings.

Namely, the color composition according to the first embodiment of thepresent invention is featured in that it comprises acrylic resin, and anorganic pigment, wherein the acrylic resin contains a copolymer formedthrough copolymerization of a first vinyl monomer having benzyl groupand a second vinyl monomer having carboxyl group and having a weightaverage molecular weight of 3000 to 11000, an acid value of solid matterof the copolymer being confined to 30 to 85.

As described above, as long as the weight average molecular weight andthe acid value of solid matter of the copolymer are confined within theaforementioned ranges, it is possible to provide the color compositionwith desirable developing properties and hence to form a pattern at anappropriate developing speed on forming color pixels by a method offorming a color filter using an alkali-soluble photosensitivecomposition.

Whereas, if the weight average molecular weight and the acid value ofsolid matter of the copolymer are not confined within the aforementionedranges, i.e. if the aforementioned weight average molecular weight isless than 3000 or more than 11000, or if the aforementioned acid valueof solid matter is less than 30 or more than 85, the viscosity of thecolor composition would be more likely to be increased with time and,furthermore, various undesirable problems would be likely to be causedto generate when an alkali-developing photosensitive compositioncontaining the color composition containing is used, the problemsincluding the deterioration of alkali-developing properties, therebymaking it impossible to appropriately regulate the developing speed,thus resulting in the prolongation of developing time or resulting intoo fast developing speed on the contrary so that the color pixels maybe easily peeled off from the surface of substrate.

Further, the first vinyl monomer having benzyl group is provided with aretardation-regulating function acting to the color layer formed throughthe curing of the color composition. Because of this, the colorcomposition according to this embodiment is capable of securing not onlyexcellent developing properties and stability but also a desiredretardation in thickness direction value (Rth).

In this case, in order to eliminate a redundant positive retardation inthickness direction value (Rth) of about 3 to +30 nm that has beengenerated due to the influence of a pigment, a dispersing agent andother kinds of binder resin and also to reduce the value Rth toward anegative value, the acrylic resin may preferably contain the vinylmonomer having benzyl group at a ratio of 76 mol % to 91 mol % based onthe solid matters of acrylic resin. By doing so, it is now possible toconfine the retardation in thickness direction value (Rth) of the colorlayer to the range of +1 to −10 nm that has been essentially desired,thereby making it possible to provide a liquid crystal display devicewhich is excellent in display properties even when the display is viewedobliquely.

Namely, when the content of the vinyl monomer having benzyl group is notless than 76 mol %, it is possible to sufficiently eliminate thepositive retardation in thickness direction value (Rth) of about 3 to+30 nm and to enable the acrylic resin to easily exhibit the functionthereof as a double refraction-regulating agent. Further, when thecontent of the vinyl monomer having benzyl group is not more than 91 mol%, it is possible to suppress the viscosity increase with time of thecolor composition.

Moreover, in order to secure a desired retardation in thicknessdirection value, the copolymer of a first vinyl monomer having benzylgroup and a second vinyl monomer having carboxyl group contained in theacrylic resin may preferably be selected from those having a weightaverage molecular weight of 2,000 to 13,000. However, in order to securenot only the aforementioned developing properties but also theaforementioned stability of the color composition, the weight averagemolecular weight thereof may more preferably be confined to 3,000 to11,000.

Incidentally, “Rth” herein is a value represented by a formula of:Rth={(Nx+Ny)/2−Nz}×d; wherein Nx is a refractive index in thex-direction in the plane of a cured film; Ny is a refractive index inthe y-direction in the plane of a cured film; and Nz is a refractiveindex in the thickness direction of the cured film. Herein, x-directionis defined as a slow axis represented by Nx≧Ny; and d is a thickness(nm) of the cured film. In the liquid crystal display device, this Rthrepresents a criterion in determining if the display properties thereofare excellent even when the display is viewed obliquely.

Next, the essential components and optional components of the colorcomposition according to this embodiment will be respectively explainedin detail.

(Acrylic Resin)

The acrylic resin to be used as an essential component of the colorcomposition according to this embodiment can be obtained through areaction using various methods such as the radical polymerizationbetween the ethylenic unsaturated group of a first vinyl monomer havingbenzyl group and the ethylenic unsaturated group of a second vinylmonomer having carboxyl group in an organic solvent. Incidentally, thefirst vinyl monomer having benzyl group is provided with aretardation-regulating function acting to the color layer formed throughthe curing of the color composition.

Examples of such a first vinyl monomer having benzyl group includebenzyl acrylate and benzyl methacrylate.

Examples of the second vinyl monomer having carboxyl group include, forexample, acrylic acid, methacrylic acid, maleic acid, monoalkyl maleicacid, fumaric acid, monoalkyl fumaric acid, itaconic acid, monoalkylitaconic acid, crotonic acid, maleic anhydride, itaconic anhydride,2-methacryloyl propionic acid, etc. Among them, acrylic acid andmethacrylic acid are more preferable for use.

In order to obtain the acrylic resin to be used in this embodiment, itis also possible to co-use, as an additional vinyl monomer other thanthe aforementioned vinyl monomers, acrylates such asalkyl(metha)acrylate including methyl(metha)acrylate,ethyl(metha)acrylate, propyl(metha)acrylate, butyl(metha)acrylate,t-butyl (metha)acrylate, benzyl(metha)acrylate, lauryl(metha)acrylate,etc.; hydroxyl group-containing (metha)acrylate such ashydroxyethyl(metha)acrylate, hydroxypropyl (metha)acrylate, etc.;ether-containing (metha)acrylate such as ethoxyethyl (metha)acrylate,glycidyl(metha)acrylate, etc.; and alicyclic (metha)acrylate such ascyclohexyl(metha)acrylate, isobornyl(metha)acrylate,dicyclopentenyl(metha)acrylate, etc., these acrylates beingco-polymerized together with the aforementioned vinyl monomers.

Incidentally, these vinyl monomers can be used singly or in combinationof two or more kinds.

Further, other kinds of compounds which can be co-polymerized togetherwith these acrylates such as styrene, cyclohexyl maleimide, phenylmaleimide, etc. can be co-used.

Furthermore, it is possible to obtain a photosensitive resin by reactinga compound having epoxy group and an unsaturated double bond such asglycidyl methacrylate with a resin that can be obtained through thecopolymerization of carboxylic acid having ethylenic unsaturated groupsuch as (metha)acrylic acid, or by addition-reacting carboxylicacid-containing compound such as (metha)acrylic acid with a resin to beobtained through the monopolymerization of epoxy-containing(metha)acrylate such as glycidyl methacrylate or through thecopolymerization of the epoxy-containing (metha)acrylate and other kindsof (metha)acrylate.

It is also possible to obtain a photosensitive resin through thereaction between a resin having hydroxyl group and constituted by amonomer such as hydroxyethyl methacrylate and a compound havingisocyanate and an ethylenic unsaturated group such asmethacryloyloxyethyl isocyanate.

Further, the color composition can be formed into a photo-curable colorcomposition for a color filter by incorporating therein aphoto-polymerizable monomer or a photo-polymerization initiator asdescribed hereinafter.

As described above, the resin to be obtained through thecopolymerization of hydroxyethyl methacrylate, etc. and having aplurality of hydroxyl groups may be reacted with a polybasic acidanhydride to introduce carboxyl group, thereby obtaining a resin havingcarboxyl group. The manufacturing method of such a resin is not limitedto the aforementioned methods.

As for specific examples of the acid anhydride to be employed in theaforementioned reactions, they include, for example, malonic anhydride,succinic anhydride, maleic anhydride, itaconic anhydride, phthalicanhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride,methyltetrahydrophthalic anhydride, trimellitic anhydride, etc.

As for specific examples of the photopolymerizable monomer, they includevarious kinds of acrylic esters and methacrylic esters such as2-hydroxyethyl(metha)acrylate, 2-hydroxypropyl(metha)acrylate,cyclohexyl(metha)acrylate, polyethyleneglycol di(metha)acrylate,pentaerythritol tri(metha)acrylate, trimethylolpropanetri(metha)acrylate, dipentaerythritol hexa(metha)acrylate,tricyclodecanyl(metha)acrylate, melamine(metha)acrylate,epoxy(metha)acrylate, etc.; (metha)acrylic acid; styrene; vinyl acetate;(metha)acryl amide; N-hydroxymethyl(metha)acryl amide; acrylonitrile;etc.

Further, it is preferable to employ polyfunctional urethane acrylatehaving (metha)acryloyl group which can be obtained through the reactionbetween (metha)acrylate having hydroxyl group and polyfunctionalisocyanate. Incidentally, the combination between the (metha)acrylatehaving hydroxyl group and polyfunctional isocyanate may be optionallyselected and hence there is not any particular limitation. Further, onlyone kind of polyfunctional urethane acrylate may be used singly or in acombination of two or more kinds thereof.

(Non-Photosensitive Resin and/or Photosensitive Resin)

The color composition according to this embodiment may constructed suchthat it includes, together with acrylic resin, a non-photosensitiveresin and/or a photosensitive resin preferably exhibiting a permeabilityof not less than 80%, more preferably not less than 95% in a totalwavelength range of 400 to 700 nm of visible light zone.

As for specific examples of the transparent resin, it is possible toemploy thermoplastic resin, thermosetting resin and photosensitiveresin. Examples of the thermoplastic resin include, for example, butyralresin, styrene-maleic acid copolymer, chlorinated polyethylene,chlorinated polypropylene, polyvinyl chloride, vinyl chloride-vinylacetate copolymer, polyvinyl acetate, polyurethane resin, polyesterresin, acrylic resin, alkyd resin, polystyrene, polyamide resin, rubbertype resin, cyclized rubber-based resin, celluloses, polybutadien,polyethylene, polypropylene, polyimide, etc. Examples of thethermosetting resin include, for example, epoxy resin, benzoguanamineresin, rosin-modified maleic resin, rosin-modified fumaric acid resin,melamine resin, urea resin, phenol resin, etc.

(Coloring Agents)

As for the coloring agent to be used in the color composition accordingto this embodiment, there is not any limitation with regard to the colortone and hence the coloring agent may be appropriately selecteddepending on the intended use of the color filter to be obtained.Namely, the coloring agent may be optionally selected from pigments,dyes and natural coloring matters.

Since the color filter is required to exhibit very high definitioncoloring and heat resistance, the coloring agents to be employed in thisembodiment may preferably be selected from those excellent in coloringproperties and in heat resistance or especially from those which arehigh in thermal decomposition resistance. Organic pigments or inorganicpigments may be preferably employed as the coloring agents. Especiallypreferable coloring agents useful in this embodiment are organicpigments and carbon black.

With respect to specific examples of the organic pigments, they include,for example, compounds which are classified as pigments in the colorindex. More specifically, the compounds which are identified by thefollowing color index (C.I.) numbers.

Namely, they include C.I. Pigment Yellow 12, C.I. Pigment Yellow 13,C.I. Pigment Yellow 14, C.I. Pigment Yellow 17, C.I. Pigment Yellow 20,C.I. Pigment Yellow 24, C.I. Pigment Yellow 31, C.I. Pigment Yellow 55,C.I. Pigment Yellow 83, C.I. Pigment Yellow 93, C.I. Pigment Yellow 109,C.I. Pigment Yellow 110, C.I. Pigment Yellow 138, C.I. Pigment Yellow139, C.I. Pigment Yellow 150, C.I. Pigment Yellow 153, C.I. PigmentYellow 154, C.I. Pigment Yellow 155, C.I. Pigment Yellow 166, C.I.Pigment Yellow 168, C.I. Pigment Yellow 180, C.I. Pigment Yellow 211;

C.I. Pigment Orange 5, C.I. Pigment Orange 13, C.I. Pigment Orange 14,C.I. Pigment Orange 24, C.I. Pigment Orange 34, C.I. Pigment Orange 36,C.I. Pigment Orange 38, C.I. Pigment Orange 40, C.I. Pigment Orange 43,C.I. Pigment Orange 46, C.I. Pigment Orange 49, C.I. Pigment Orange 61,C.I. Pigment Orange 64, C.I. Pigment Orange 68, C.I. Pigment Orange 70,C.I. Pigment Orange 71, C.I. Pigment Orange 72, C.I. Pigment Orange 73,C.I. Pigment Orange 74;

C.I. Pigment Red 1, C.I. Pigment Red 2, C.I. Pigment Red 5, C.I. PigmentRed 17, C.I. Pigment Red 31, C.I. Pigment Red 32, C.I. Pigment Red 41,C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 144, C.I.Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 168, C.I.Pigment Red 170, C.I. Pigment Red 171, C.I. Pigment Red 175, C.I.Pigment Red 176, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I.Pigment Red 179, C.I. Pigment Red 180, C.I. Pigment Red 185, C.I.Pigment Red 187, C.I. Pigment Red 202, C.I. Pigment Red 206, C.I.Pigment Red 207, C.I. Pigment Red 209, C.I. Pigment Red 214, C.I.Pigment Red 220, C.I. Pigment Red 221, C.I. Pigment Red 224, C.I.Pigment Red 242, C.I. Pigment Red 243, C.I. Pigment Red 254, C.I.Pigment Red 255, C.I. Pigment Red 262, C.I. Pigment Red 264, C.I.Pigment Red 272;

C.I. Pigment Violet 1, C.I. Pigment Violet 19, C.I. Pigment Violet 23,C.I. Pigment Violet 29, C.I. Pigment Violet 32, C.I. Pigment Violet 36,C.I. Pigment Violet 38;

C.I. Pigment Blue 15, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4,C.I. Pigment Blue 15:6, C.I. Pigment Blue 60, C.I. Pigment Blue 80;

C.I. Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Green 58;

C.I. Pigment Brown 23, C.I. Pigment Brown 25;

C.I. Pigment Black 1, C.I. Pigment Black 7.

These organic pigments can be used after refining them by means of, forexample, a sulfuric acid re-crystallization method, a solvent washingmethod, a salt-milling method or a combination thereof.

Among these organic pigments, it is more preferable to employ at leastone kind of organic pigments selected from the group consisting of C.I.Pigment Yellow 83, C.I. Pigment Yellow 139, C.I. Pigment Yellow 138,C.I. Pigment Yellow 150, C.I. Pigment Yellow 180, C.I. Pigment Red 166,C.I. Pigment Red 177, C.I. Pigment Red 242, C.I. Pigment Red 254, C.I.Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:6, C.I.Pigment Green 7, Pigment Green 36, C.I. Pigment Green 58, C.I. PigmentViolet 23, C.I. Pigment Blue 60 and C.I. Pigment Blue 80.

Although there is not any particular limitation with regard to themixing ratio of the pigment, the pigment may preferably be incorporatedat a ratio of 5-70% by weight based on a total quantity (100% by weight)of the color composition. More preferably, the pigment may beincorporated at a ratio of about 5-50% by weight, most preferably about20-50% by weight, the balance being substantially constituted by aresinous binder that can be provided by a pigment carrier.

Further, for the purpose of spectral adjustment of color filter, thesecoloring agents may be used in combination of two or more kinds thereof.These coloring agents may be incorporated in the color composition at aratio of 5-70% by weight based on a total quantity (100% by weight) ofthe solid matters of the color composition.

Further, in order to secure excellent coating properties, sensitivity,developing properties while making it possible to retain balance betweenthe chroma and brightness, the aforementioned organic pigments may beused in combination with inorganic pigments. As for the inorganicpigments, it is possible to employ metal oxide powder, metal sulfidepowder or metal powder such as yellow lead, zinc yellow, red iron oxide(III), cadmium red, ultramarine blue, Prussian blue, chromium oxidegreen, cobalt green, etc. For the purpose of toning, the colorcomposition may further contain dyes within the limits which do notdeteriorate the heat resistance of the color composition.

(Dispersing Agent)

When the pigment is dispersed in a pigment carrier and in an organicsolvent, a dispersing agent or a surfactant is required to be used forthe dispersion of the pigment. With respect to the dispersing agent, itis possible to employ a surfactant, an intermediate of pigment, anintermediate of dye, a Solsperse, etc. These dispersing agents arerespectively provided with not only a pigment affinity moiety exhibitingpigment-adsorbing properties, but also another moiety exhibitingcompatibility to a pigment carrier, thereby enabling the dispersingagents to adsorb onto the pigment and to stabilize the dispersion of thepigment in the pigment carrier.

As for specific examples of the dispersing agent, they includepolyurethane, polycarboxylate such as polyacrylate, unsaturatedpolyamide, polycarboxylic acid, (partial) amine polycarboxylate,ammonium polycarboxylate, alkyl amine polycarboxylate, polysiloxane,long chain polyaminoamide phosphate, hydroxyl group-containingpolycarboxylate and modified compounds thereof, an oily dispersing agentsuch as amide to be formed through a reaction between poly(lower alkylimine) and polyester having a free carboxyl group and salts of theamide, (metha)acrylic acid-styrene copolymer, (metha)acrylicacid-(metha)acrylate copolymer, styrene-maleic acid copolymer,water-soluble resin or water-soluble macromolecular compound such aspolyvinyl alcohol and poly(vinyl pyrrolidone), polyester compounds,modified polyacrylate compounds, ethylene oxide/propylene oxide adduct,phosphate, etc. These compounds may be employed individually or incombination of two or more kinds.

These dispersing agents are available on the market. Specific examplesof them include, for example, Disperbyk-2000 and Disperbyk-2001 (allavailable from BigChemy (BYK) Co., Ltd.) each representing a modifiedacrylic copolymer; Disperbyk-161, Disperbyk-162, Disperbyk-165,Disperbyk-167, Disperbyk-170, Disperbyk-182 (all available from BigChemy(BYK) Co., Ltd.), SOLSPERSE-76500 (available from Lubrizole Co., Ltd.)each representing polyurethane; SOLSPERSE-24000, SOLSPERSE-37500 (allavailable from Lubrizole Co., Ltd.), Ajisper PB821, Ajisper PB822,Ajisper PB880 (all available from Ajinomoto Fine Techno Co., Ltd.) eachrepresenting a cationic tandem type graft polymer.

Although there is not any particular limitation with regard to themixing ratio of the dispersing agent, it is preferable to incorporatethe dispersing agent at a ratio of 1 to 10% by weight based on 100% byweight of the quantity of pigments. Further, The color composition maypreferably be formulated such that bulky particles 5 μm or more in size,preferably, bulky particles 1 μm or more in size, more preferably, bulkyparticles 0.5 μm or more in size as well as dusts intermingled thereinare completely removed from the composition by making use of centrifugalseparation, sintered filter, membrane filter, etc.

(Surfactants)

As for the surfactant, it is possible to employ an anionic surfactantsuch as polyoxyethylene alkylether sulfate, dodecylbenzene sodiumsulfonate, alkali salts of styrene-acrylic acid copolymer,alkylnaphthaline sodium sulfonate, alkyldiphenyl ether sodiumdisulfonate, monoethanol amine lauryl sulfate, triethanol amine laurylsulfate, ammonium lauryl sulfate, monoethanol amine stearate, sodiumstearate, sodium lauryl sulfate, monoethanol amine of styrene-acrylicacid copolymer, polyoxyethylene alkylether phosphate, etc.; a nonionicsurfactant such as polyoxyethylene oleyl ether, polyoxyethylene laurylether, polyoxyethylene nonylphenyl ether, polyoxyethylene alkyletherphosphate, polyoxyethylene sorbitan monostearate, polyethyleneglycolmonolaurate, etc.; cationic surfactant such as alkyl quaternary ammoniumsalt and an ethylene oxide adduct thereof, etc.; and an amphotericsurfactant such as alkyl betaine such as betaine alkyldimethylaminoacetate, alkylimidazoline, etc. These surfactants can be employedsingly or in combination of two or more kinds.

(Photo-Polymerization Initiators)

As for specific examples of the photo-polymerization initiator, theyinclude an acetophenone-based compound such as 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone,diethoxyacetophenone,1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one,1-hydroxycyclohexylphenyl ketone,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one; abenzoin-based compound such as benzoin, benzoin methyl ether, benzoinethyl ether, benzoin isopropyl ether, benzyldimethyl ketal, etc.; abenzophenone-based compound such as benzophenone, benzoylbenzoic acid,benzoylmethyl benzoate, 4-phenyl benzophenone, hydroxybenzophenone,acrylated benzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, etc.; athioxanthone-based compound such as thioxanthone, 2-chlorothioxanthone,2-methylthioxanthone, isopropylthioxanthone,2,4-diisopropylthioxanthone, etc.; a triazine-based compound such as2,4,6-trichloro-s-triazine,2-phenyl-4,6-bis(trichloromethyl)-s-triazine,2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine,2-piperonyl-4,6-bis(trichloromethyl)-s-triazine,2,4-bis(trichloromethyl)-6-styryl-s-triazine,2-(naphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine,2-(4-methoxynaphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine,2,4-trichloromethyl-(piperonyl)-6-triazine,2,4-trichloromethyl(4′-methoxystyryl)-6-triazine, etc.; anO-acyloxime-based compound such as1-[4-(phenylthio)-2-(O-benzoyloxime)],O-(acetyl)-N-(1-phenyl-2-oxo-2-(4′-methoxynaphthyl)ethylidene)hydroxylamine,1-[4-(phenylthio)phenyl]-heptan-1,2-dione-2-(O-benzoyloxime),1-[4-(phenylthio)phenyl]-octan-1,2-dione-2-(O-benzoyloxime),1-[4-(benzoyl)phenyl]-octan-1,2-dione-2-(O-benzoyloxime),1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone-1-(O-acetyloxime),1-[9-ethyl-6-(3-methylbenzoyl)-9H-carbazol-3-yl]-ethanone-1-(O-acetyloxime),1-(9-ethyl-6-benzoyl-9.H.-carbazol-3-yl]-ethanone-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydrofuranylbenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydropyranylbenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-5-tetrahydrofuranylbenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-5-tetrahydropyranylbenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxoranyl)benzoyl}-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydrofuranylmethoxybenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydropyranylmethoxybenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-5-tetrahydrofuranylmethoxybenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-5-tetrahydropyranylmethoxybenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxoranyl)methoxybenzoyl}-9.H.-carbazol-3-yl]-1-(O-acetyloxime),etc.; a phosphine-based compound such asbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc.; a quinone-based compound such as9,10-phenanthrene quinone, camphor quinone, ethyl anthraquinone, etc.; aborate-based compound; a carbazol-based compound; an imidazole-basedcompound, titanocene-based compound, etc. Among these O-acyloxime-basedcompounds, especially preferable examples thereof include1-[4-(phenylthio)phenyl]-octan-1,2-dione-2-(O-benzoyloxime),1-[9-ethyl-6-(2-methylbenzoyl-9.H.-carbazol-3-yl]-ethanone-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-(2-methyl-4-tetrahydrofuranylmethoxybenzoyl)-9.H.-carbazol-3-yl]-1-(O-acetyloxime),ethanone-1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxoranyl)methoxybenzoyl}-9.H.-carbazol-3-yl]-1-(O-acetyloxime),etc. These photo-polymerization initiators can be employed singly or incombination of two or more kinds thereof.

(Photo-Sensitizer)

It is preferable to use these photo-polymerization initiators incombination with a photo-sensitizer. Specific examples of thephoto-sensitizer include α-acyloxy ester, acylphosphine oxide,methylphenyl glyoxylate, benzyl, 9,10-phenanthrene quinone, camphorquinone, ethylanthraquinone, 4,4′-diethyl isophthalophenone,3,3′,4,4′-tetra(t-butyl peroxycarbonyl)benzophenone, 4,4′-diethylaminobenzophenone, etc.

These sensitizers can be employed at a ratio of 0.1 to 60 parts byweight based on 100 parts by weight of the photo-polymerizationinitiator.

(Solvents)

The color composition according to this embodiment may further contain asolvent such as water, organic solvents, etc. for enabling the colorcomposition to be uniformly coated on the surface of a substrate.Further, in the case where the color composition according to thisembodiment is to be used for constituting the color layer of colorfilter, the solvent acts to enable pigments to be uniformly dispersed inthe color layer. Specific examples of the solvent include, for example,cyclohexanone, ethyl Cellosolve acetate, butyl Cellosolve acetate,1-methoxy-2-propyl acetate, diethyleneglycol dimethyl ether, ethylbenzene, ethyleneglycol diethyl ether, xylene, ethyl Cellosolve,methyl-n amyl ketone, propyleneglycol monomethyl ether, toluene,methylethyl ketone, ethyl acetate, methanol, ethanol, isopropyl alcohol,butanol, isobutyl ketone, petroleum solvent, etc. These solvents may beemployed singly or in combination of two or more kinds.

The mixing ratio of these solvents may be confined to the range of 800to 4,000 parts by weight, preferably 1,000 to 2,500 parts by weightbased on 100 parts by weight of the pigments in the color composition.

(Method of Preparing Color Composition)

The color composition according to this embodiment can be prepared byway of any conventional method. For example, a photosensitive colorcomposition containing a photo-polymerizable monomer, acrylic resin, acoloring agent, a dispersing agent and a solvent may be preparedaccording to the following methods.

(1) A pigment composition that has been prepared in advance through themixing of a coloring agent with a dispersing agent is added to anddispersed in a mixture of a photo-polymerizable monomer and acrylicresin or in a solution obtained by dissolving these components in asolvent. Then, residual components are added to the resultantdispersion.

(2) A coloring agent and a dispersing agent are individually added toand dispersed in a mixture of a photo-polymerizable monomer and acrylicresin or in a solution obtained by dissolving these components in asolvent. Then, residual components are added to the resultantdispersion.

(3) A coloring agent is added to and dispersed in a mixture of aphoto-polymerizable monomer and acrylic resin or in a solution obtainedby dissolving these components in a solvent. Then, a dispersing agent isadded to the resultant solution and then residual components are addedto the resultant dispersion.

(4) Two kinds of mixtures each containing a photo-polymerizable monomerand acrylic resin or two kinds of solutions each obtained by dissolvingthese components in a solvent are prepared in advance and then acoloring agent and a dispersing agent are separately dispersed inaforementioned two kinds of materials. Then, these dispersions are mixedtogether and then residual components are added to the resultantdispersion. Incidentally, either the coloring agent or the dispersingagent may be dissolved only in the solvent.

Herein, the dispersion of the coloring agent and the dispersing agent ina mixture of a photo-polymerizable monomer and acrylic resin or in asolution obtained by dissolving these components in a solvent may beperformed by making use of various kinds of dispersing apparatus such asa triple roll mill, a twin-roll mill, a sand mill, a kneader, adissolver, a high-speed mixer, a homomixer, an attritor, etc. Further,in order to execute the dispersion more preferably, the dispersion maybe performed with addition of various kinds of surfactant.

Although, when a color composition is prepared using a pigmentcomposition obtained by mixing a coloring agent and a dispersing agent,the mixing may be performed by simply mixing a powdery coloring agentwith a powdery dispersing agent, it is more preferable to employ thefollowing mixing methods, i.e. (a) a mechanical mixing method usingvarious kinds of grinders such as a kneader, a roll, an attritor, asuper mill, etc.; (b) a method wherein a pigment is dispersed in asolvent to obtain a dispersion to which a solution containing adispersing agent is added, thereby enabling the dispersing agent to beadsorbed onto the surface of pigment; (c) a method wherein a pigment anda dispersing agent are co-dissolved in a solvent exhibiting a strongdissolving power such as sulfuric acid and then co-precipitation isexecuted by making use of a poor solvent such as water, etc.

Next, there will be explained about the color filter according to asecond embodiment of the invention wherein the color compositionaccording to the first embodiment of the present invention explainedabove is employed.

FIG. 1 is a cross-sectional view schematically illustrating the colorfilter according to the second embodiment of the present invention.

As shown in FIG. 1, a black matrix 2 which is obtained through thepatterning of a metal layer made of chromium or a photo-sensitive blackresin composition is formed on the surface of a substrate 1 by means ofthe conventional method. As for the substrate 1 to be employed herein,it is preferable to use a transparent substrate such as a glasssubstrate or a resinous substrate made of polycarbonate, poly-methylmethacrylate, polyethylene phthalate, etc. Further, for the purpose ofdriving the liquid crystal molecules after the fabrication of a liquidcrystal panel, a transparent electrode consisting of a combination ofmetal oxides such as indium oxide, tin oxide, zinc oxide, gallium oxideand antimony oxide may be formed on the surface of a glass plate or aresinous plate.

First of all, the color composition according to one embodiment of thepresent invention is uniformly coated on the surface of the substrate 1by any desired coating method such as spray coating, spin coating, rollcoating, etc., thereby forming a layer, which is then dried to form acolor composition layer. Then, by means of photolithography, the colorcomposition layer thus formed is subjected to a patterning process.Namely, the color composition layer is exposed to the irradiation of anactive energy beam such as ultraviolet rays, electron beam, etc. througha photomask having a desired light-shielding pattern and then theresultant color composition layer is subjected to a developing processby making use of a developing solution such as an organic solvent or analkali aqueous solution. As a result of this exposure process, thephoto-polymerizable monomer located on the regions irradiated with theactive energy beam is allowed to polymerize and cure. Further, when thecolor composition contains a photosensitive resin, this photosensitiveresin is allowed to cross-link and cure.

Further, in order to enhance the exposure sensitivity, a water-solubleor alkali-soluble resin (for example, polyvinyl alcohol or awater-soluble acrylic resin) may be coated, prior to the step ofexposure, on the surface of the coated photosensitive color compositionand dried, thereby forming a film which is capable of suppressing theeffects of oxygen to obstruct the polymerization.

In the step of the development, the portions of the color compositionlayer which are not irradiated with the active energy beam is washed outby making use of a developing solution to obtain a desired pattern. Asfor the method of developing treatment, it is possible to employ ashower developing method, a spray developing method, a dip developingmethod, a paddle developing method, etc. Incidentally, with respect tothe developing solution, an alkali developing solution such as anaqueous solution of sodium carbonate, sodium hydroxide, etc. or anorganic alkaline solution such as dimethylbenzyl amine, triethanolamine, etc. may be mainly employed. Further, if required, the developingsolution may contain a defoaming agent or a surfactant.

Thereafter, the resultant layer thus developed is baked, and the sameprocedures as described above are repeated for other colors, thusmanufacturing a color filter. More specifically, color pixels 3consisting of red color pixels 3R, green color pixels 3G and blue colorpixels 3B are formed on the surface of substrate 1 having a black matrix2 formed thereon. Moreover, in order to make uniform the cell gap ofliquid crystal display device, a spacer (not shown) may be formed onthese color pixels 3.

Next, there will be explained about the liquid crystal display deviceaccording to a third embodiment of the invention wherein the colorfilter according to the second embodiment of the present inventionexplained above is employed.

FIG. 2 is a cross-sectional view schematically illustrating the liquidcrystal display device according to a third embodiment of the presentinvention.

The liquid crystal display device 7 shown in FIG. 2 illustrates atypical example of a TFT drive type liquid crystal display device foruse in a notebook-sized personal computer. This liquid crystal displaydevice 4 is provided with a pair of transparent substrates 5 and 6,which are arranged face to face with a gap interposed therebetween. Thegap between them is filled with a LC (liquid crystal).

The liquid crystal display device according to this embodiment of theinvention can be applied to various liquid crystal alignment modes suchas TN (Twisted Nematic), STN (Super Twisted Nematic), IPS (In-Planeswitching), VA (Vertical Alignment), OCB (Optically CompensatedBirefringence), etc.

On the inner surface of the first transparent substrate 5, there isformed a TFT (thin film transistor) array 7. On this TFT array 7 isdeposited a transparent electrode layer 8 formed of ITO for example. Onthis transparent electrode layer 8 is further provided an alignmentlayer 9. Further, a polarizer (polarizing plate) 10 comprising aretardation film is formed on the outer surface of the transparentsubstrate 5.

On the other hand, on the inner surface of the second transparentsubstrate 6, there is formed a color filter 11 shown in FIG. 1. Thefilter segments of red pixels, green pixels and blue pixels constitutingthe color filter 11 are separated from each other by a black matrix (notshown). If required, a transparent protective film (not shown) may beformed so as to cover the color filter 11. Furthermore, a transparentelectrode layer 12 consisting of ITO for example is formed on thisprotective film. An alignment layer 13 is deposited so as to cover thetransparent electrode layer 12. Further, a polarizer 14 is formed on theouter surface of the transparent substrate 6. Incidentally, a back lightunit 16 equipped with a triple wavelength lamp 15 is disposed below thepolarizer 10. The triple wavelength lamp employed as a light source maybe replaced by a light-emitting diode or by an organic EL device.

EXAMPLES

Although the present invention will be explained below by referring tospecific examples of the present invention and to comparative examples,it may not be construed that the present invention is limited to theseexamples. Further, since the materials to be employed in these examplesare very sensitive to light, it may be required to prevent thesensitization of the materials by redundant light such as natural light,so that every works were performed under the yellow or red lamp.Incidentally, “part(s)” in the following examples and comparativeexamples means “weight part(s)”. Further, the symbols of pigments areindicated by a color index number. For example, “PG36” means “C.I.Pigment Green 36”, and “PY150” means “C.I. Pigment Yellow 150”.

(Preparation of Resinous Solutions)

The polymer compositions to be employed in Examples and ComparativeExamples were prepared as follows by making use of a first vinyl monomerhaving benzyl group and a second vinyl monomer having carboxyl group.The weight average molecular weight of the polymer compositions in thepresent invention was a weight average molecular weight reduced aspolystyrene and measured by means of gel permeation chromatography. Morespecifically, the weight average molecular weight can be determinedbased on a calibration curve which is prepared by making use of standardpolystyrene exhibiting monodispersion indicating 1 (actually, not morethan 1.10) in the ratio (degree of dispersion) between a weight averagemolecular weight (Mw) and a number average molecular weight (Mn),wherein the molecular weight of a sample measured by making use of a gelpermeation chromatography device is allocated to the molecular weight inthe calibration curve. The weight average molecular weight (Mw) can becalculated according to the following calculation formula. Incidentally,the weight average molecular weight that has been detected by making useof a data processing apparatus is generally employed.Weight average molecular weight (Mw)=Σ(Wi×Mi)/W=Σ(Hi×Mi)/ΣHi

(wherein W is a total weight of a polymer; Wi is a weight of the “i”thpolymer; Mi is a molecular weight at the “i”th elution time; and Hi is aheight at the “i”th elution time)

Followings are details of the measuring apparatus and measuringconditions.

Measuring apparatus (Gel permeation chromatography)

Apparatus: HLC-8220GPC (Tohso Co., Ltd.)

Columns Used:

TSKgel G2000H_(XL) (Tohso Co., Ltd.) (Column 1)

TSKgel G3000H_(XL) (Tohso Co., Ltd.) (Column 2)

TSKgel G4000H_(XL) (Tohso Co., Ltd.) (Column 3)

TSKgel G5000H_(XL) (Tohso Co., Ltd.) (Column 4)

Guard column H_(XL)-H (Tohso Co., Ltd.) (Column 6)

Connection of columns: A system connected in the order of (Column 6),(Column 4), (Column 3), (Column 2) and (Column 1) was used.

Detector: R1 (Differential refractometer)

Data processing: Multi-station 8020 (Tohso Co., Ltd.)

Preparation of standard polystyrene: Samples each weighing 10 mg weretaken up respectively from 5 or 6 kinds of standard polystyrenediffering in molecular weight from each other and dissolved respectivelyin 100 mL of tetrahydrofuran (hereinafter referred to as THF). Thedissolution was conducted at a temperature of 20° C. and then left tostand for 24 hours before use.

Preparation of samples: Samples each weighing 80 mg were taken uprespectively and dissolved in 20 mL of THF.

Conditions for the Measurement:

Temperature of columns: 40° C.

Solvent: THF

Flow rate: 1 mL/min.

Amount injected of samples: 100 μL

Synthesis Example 1 Polymer Composition 1

1,540 parts of propyleneglycol monomethylether acetate (hereinafterreferred to as PGMAc) were introduced into a four-necked flask equippedwith a stirrer, a thermometer, a cooling tube and a nitrogen-introducingtube. After the PGMAc was heated up to 110° C. under a nitrogen gasstream, a mixed solution consisting of 950 parts of benzyl methacrylate,one part of methacrylic acid, 49 parts of acrylic acid and 100 parts oft-butylperoxy-2-ethylhexanoate (hereinafter referred to as TBPEH) wasadded drop-wise to the PGMAc taking 4 hours. After finishing theaddition of the mixed solution, the resultant mixture was subjected toreaction for 9 hours at 110° C., thereby obtaining a solution of polymercontaining 40% of nonvolatile matters and having a weight averagemolecular weight of 4,296. This polymer composition will be referred toas Polymer composition 1.

Synthesis Example 2 Polymer Composition 2

1,520 parts of PGMAc were introduced into the same kind of four-neckedflask as employed in Synthesis Example 1. After the PGMAc was heated upto 135° C. under a nitrogen gas stream, a mixed solution consisting of950 parts of benzyl methacrylate, one part of methacrylic acid, 49 partsof acrylic acid, 30 parts of TBPEH and 2 parts of di-t-butylperoxide wasadded drop-wise to the PGMAc taking 5 hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 2 hours at 135° C. and then for 5hours at 120° C., thereby obtaining a solution of polymer containing 40%of nonvolatile matters and having a weight average molecular weight of7,029. This polymer composition will be referred to as Polymercomposition 2.

Synthesis Example 3 Polymer Composition 3

1,540 parts of PGMAc were introduced into the same kind of four-neckedflask as employed in Synthesis Example 1. After the PGMAc was heated upto 110° C. under a nitrogen gas stream, a mixed solution consisting of870 parts of benzyl methacrylate, 130 parts of methacrylic acid and 30parts of TBPEH was added drop-wise to the PGMAc taking 4 hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 9 hours at 110° C., therebyobtaining a solution of polymer containing 40% of nonvolatile mattersand having a weight average molecular weight of 10,568. This polymercomposition will be referred to as Polymer composition 3.

Synthesis Example 4 Polymer Composition 4

1,540 parts of PGMAc were poured into the same kind of four-necked flaskas employed in Synthesis Example 1. After the PGMAc was heated up to110° C. under a nitrogen gas stream, a mixed solution consisting of 870parts of benzyl methacrylate, 130 parts of methacrylic acid and 100parts of TBPEH was added drop-wise to the PGMAc taking 4 hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 9 hours at 110° C., therebyobtaining a solution of polymer containing 40% of nonvolatile mattersand having a weight average molecular weight of 4327. This polymercomposition will be referred to as Polymer composition 4.

Synthesis Example 5 Polymer Composition 5

1,540 parts of cyclohexanone were introduced into the same kind offour-necked flask as employed in Synthesis Example 1. After thecyclohexanone was heated up to 110° C. under a nitrogen gas stream, amixed solution consisting of 950 parts of benzyl methacrylate, 50 partsof methacrylic acid and 100 parts of TBPEH was added drop-wise to thecyclohexanone taking 4 hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 8 hours at 110° C., therebyobtaining a solution of polymer containing 40% of nonvolatile mattersand having a weight average molecular weight of 4,173. This polymercomposition will be referred to as Polymer composition 5.

Synthesis Example 6 Polymer Composition 6

1,540 parts of PGMAc were introduced into the same kind of four-neckedflask as employed in Synthesis Example 1. After the cyclohexanone washeated up to 110° C. under a nitrogen gas stream, a mixed solutionconsisting of 950 parts of benzyl methacrylate, 50 parts of methacrylicacid and 30 parts of TBPEH was added drop-wise to the PGMAc taking 4hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 9 hours at 110° C., therebyobtaining a solution of polymer containing 40% of nonvolatile mattersand having a weight average molecular weight of 10,097. This polymercomposition will be referred to as Polymer composition 6.

Synthesis Example 7 Polymer Composition 7

1,540 parts of PGMAc were introduced into the same kind of four-neckedflask as employed in Synthesis Example 1. After the cyclohexanone washeated up to 110° C. under a nitrogen gas stream, a mixed solutionconsisting of 950 parts of benzyl methacrylate, 50 parts of methacrylicacid and 22 parts of TBPEH was added drop-wise to the PGMAc taking 4hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 9 hours at 110° C., therebyobtaining a solution of polymer containing 40% of nonvolatile mattersand having a weight average molecular weight of 12,822. This polymercomposition will be referred to as Polymer composition 7.

Synthesis Example 8 Polymer Composition 8

1,540 parts of PGMAc were introduced into the same kind of four-neckedflask as employed in Synthesis Example 1. After the cyclohexanone washeated up to 110° C. under a nitrogen gas stream, a mixed solutionconsisting of 870 parts of benzyl methacrylate, 130 parts of methacrylicacid and 20 parts of t-amylperoxy-2-ethylhexanoate was added drop-wiseto the PGMAc taking 4 hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 9 hours at 110° C., therebyobtaining a solution of polymer containing 40% of nonvolatile mattersand having a weight average molecular weight of 14,000. This polymercomposition will be referred to as Polymer composition 8.

Synthesis Example 9 Polymer Composition 9

1,540 parts of PGMAc were poured into the same kind of four-necked flaskas employed in Synthesis Example 1. After the cyclohexanone was heatedup to 110° C. under a nitrogen gas stream, a mixed solution consistingof 870 parts of benzyl methacrylate, one part of methacrylic acid, 129parts of acrylic acid and 100 parts of TBPEH was added drop-wise to thePGMAc taking 4 hours. After finishing the addition of the mixedsolution, the resultant mixture was subjected to reaction for 9 hours at110° C., thereby obtaining a solution of polymer containing 40% ofnonvolatile matters and having a weight average molecular weight of4,670. This polymer composition will be referred to as Polymercomposition 9.

Synthesis Example 10 Polymer Composition 10

1,520 parts of PGMAc were introduced into the same kind of four-neckedflask as employed in Synthesis Example 1. After the PGMAc was heated upto 135° C. under a nitrogen gas stream, a mixed solution consisting of960 parts of benzyl methacrylate, 40 parts of methacrylic acid, 30 partsof TBPEH and 2 parts of di-t-butylperoxide was added drop-wise to thePGMAc taking 5 hours.

After finishing the addition of the mixed solution, the resultantmixture was subjected to reaction for 2 hours at 135° C. and then for 6hours at 125° C., thereby obtaining a solution of polymer containing 40%of nonvolatile matters and having a weight average molecular weight of7,513. This polymer composition will be referred to as Polymercomposition 10.

The results obtained are shown in the following Table 1.

TABLE 1 Content of first vinyl monomer having benzyl (mol %/solid Weightaverage Acid value of matter of resin) Solvents molecular weight solidmatters Polymer composition 1 88.6 PGMAc 4,296 39.4 Polymer composition2 88.6 PGMAc 7,029 41.6 Polymer composition 3 76.6 PGMAc 10,568 81.0Polymer composition 4 76.6 PGMAc 4,327 82.5 Polymer composition 5 90.3Cyclohexanone 4,173 31.1 Polymer composition 6 90.3 PGMAc 10,097 33.3Polymer composition 7 90.3 PGMAc 12,822 33.2 Polymer composition 8 76.6PGMAc 14,000 82.5 Polymer composition 9 73.3 PGMAc 4,670 94.2 Polymercomposition 10 92.1 PGMAc 7,513 27.9

Preparation of Pigment Dispersion Preparation Example 1

20 parts of a mixture of C.I. Pigment Red 254/C.I. Pigment Red 177(weight ratio: 80/20) as a coloring agent, 5 parts (calculated as asolid matter) of BYK-2001 as a dispersing agent, and 75 parts ofpropylene glycol monomethylether acetate as a solvent were treated in abeads mill to prepare a pigment dispersion (R).

Preparation Example 2

20 parts of a mixture of C.I. Pigment Green 36/C.I. Pigment Yellow 150(weight ratio: 50/50) as a coloring agent, 5 parts (calculated as asolid matter) of SOLSPERSE-24000 as a dispersing agent, and 75 parts ofpropylene glycol monomethylether acetate as a solvent were treated in abeads mill to prepare a pigment dispersion (G).

Preparation Example 3

20 parts of a mixture of C.I. Pigment Blue 15:6/C.I. Pigment Violet 23(weight ratio: 96/4) as a coloring agent, 5 parts (calculated as a solidmatter) of Ajisper PB-821 as a dispersing agent, and 75 parts ofpropylene glycol monomethylether acetate as a solvent were treated in abeads mill to prepare a pigment dispersion (B).

Example 1

A blue color composition to be used for manufacturing a color filteraccording to the following procedures was prepared.

<Blue Color Composition>

A mixture having the following composition was agitated to obtain auniform mixture and then the resultant mixture was filtered using a 5μm-mesh filter to obtain Blue color composition 1.

Above-described pigment dispersion (B) 42 parts Polymer composition 1 10parts Trimethylolpropane triacrylate 4.8 parts Photopolymerizationinitiator 2.8 parts (“IRGACURE-369”, Ciba-Geigy Co., Ltd.)Photo-sensitizer 0.2 part (“EAB-F”, Hodogaya Kagaku Co., Ltd.)Cyclohexanone 40.2 parts

Examples 2 to 8, Comparative Examples 1 to 6

The color compositions 2 to 14 were obtained by repeating the sameprocedure as described in Example 1 except that the pigment dispersionand the resin contained in the color composition were replaced by thepigment dispersions and the resins described in the following Table 2.Incidentally, the color compositions of Comparative Examples 7 to 9 (thecolor compositions 15 to 17) were those which did not contain thecopolymers to be used in the present invention.

TABLE 2 Pigment disper- Polymer composition sion in color compositionEx. 1 Color composition 1 B Polymer composition 1 Ex. 2 Colorcomposition 2 B Polymer composition 2 Ex. 3 Color composition 3 BPolymer composition 3 Ex. 4 Color composition 4 B Polymer composition 4Ex. 5 Color composition 5 B Polymer composition 5 Ex. 6 Colorcomposition 6 B Polymer composition 6 Ex. 7 Color composition 7 GPolymer composition 1 Ex. 8 Color composition 8 R Polymer composition 1Comp. Ex. 1 Color composition 9 B Polymer composition 7 Comp. Ex. 2Color composition 10 B Polymer composition 8 Comp. Ex. 3 Colorcomposition 11 B Polymer composition 9 Comp. Ex. 4 Color composition 12B Polymer composition 10 Comp. Ex. 5 Color composition 13 G Polymercomposition 7 Comp. Ex. 6 Color composition 14 R Polymer composition 7Comp. Ex. 7 Color composition 15 R — Comp. Ex. 8 Color composition 16 G— Comp. Ex. 9 Color composition 17 B —

The color compositions according to the aforementioned Examples andComparative Examples were evaluated by measuring the followingcharacteristics.

1. Assessment of Long-Term Storage Stability

The initial viscosity of a green color composition which was preparedthe day before and the aged viscosity of the same green colorcomposition which was aged for one week at 40° C. were measured bymaking use of an E-type viscometer (ELD type viscometer, Toki SangyoCo., Ltd.) under the conditions of: 25° C. in temperature and 20 rpm inrevolving speed. Based on the values of the initial viscosity and of theaged viscosity, the rate of change of the viscosity with time wascalculated.[Rate of change of the viscosity with time]=|{(initial viscosity)−(agedviscosity)}/(initial viscosity)|×100

The assessment of the long-term storage stability was performed based onthe following standard.

∘: 10% or less in the rate of change of the viscosity with time

Δ: More than 10% and not more than 20% in the rate of change of theviscosity with time

x: More than 20% in the rate of change of the viscosity with time

2. Retardation in Thickness Direction (Rth)

Each of color layers was manufactured according to the followingprocedure and the values of retardation in thickness direction weremeasured.

By means of spin coating, each of color resists shown in above Table 2was coated on the surface of a glass substrate and then pre-baked for 20minutes in a clean oven at a temperature of 70° C. Then, after beingcooled to room temperature, the substrate was exposed to ultravioletrays by making use of an ultra-high pressure mercury lamp. Thereafter,the resultant substrate was subjected to spray development by making useof an aqueous solution of sodium carbonate heated up to 23° C., afterwhich the resultant substrate was washed with ion-exchanged water andair-dried. Subsequently, the resultant substrate was post-baked for 30minutes in a clean oven at a temperature of 230° C., thereby forming acolored coated film of each of colors. The film thickness as dried ofthe coated film was 1.8 μm in every case.

The values of retardation in thickness direction were determined asfollows. Namely, by making use of a retardation in thickness directionmeasuring apparatus (“RETS-100”; Ohtsuka Denshi Co., Ltd.), theretardation Δ(λ) of the color layer was measured from the directionwhich was angled by 45° from the normal direction of substrate havingthe color layer formed thereon. Then, by making use of this value, thethree-dimensional refractive index was calculated and, based on thisthree-dimensional refractive index, the value Rth of retardation inthickness direction was calculated according to the following equation(1). In this case, a wavelength of 610 nm was used for the red colorlayer, a wavelength of 550 nm was used for the green color layer, and awavelength of 450 nm was used for the blue color layer.Rth={(Nx+Ny)/2−Nz}×d  (1)

(wherein Nx is a refractive index in the direction of x in the plane ofcolor layer; Ny is a refractive index in the direction of y in the planeof color layer; and Nz is a refractive index in the thickness-wisedirection of color layer; x being defined as a slow axis represented byNx≧Ny; and d is a thickness (nm) of color layer.

The following Table 3 illustrates the value Rth of retardation inthickness direction of each of color layers which were manufactured bymaking use of each of color resists shown in above Table 2. As the valueRth of retardation in thickness direction of the retardation plate andliquid crystal material to be used in a liquid crystal display devicewas combined with the value Rth of retardation in thickness direction ofthe color layer, if it was aimed to minimize the black discoloration ofa liquid crystal display device at the off state as it is viewedobliquely, the value Rth of retardation in thickness direction of eachof color layers was: +1 nm to −8 nm in the case of a red film, +0 nm to−10 nm in the case of a green film, and +1 nm to −8 nm in the case of ablue film.

The retardation in thickness direction value of the color layer wasevaluated according to the following standard.

∘: The retardation in thickness direction value was confined to +1 nm to−8 nm in the case of a red film, +0 nm to −10 nm in the case of a greenfilm, and +1 nm to −8 nm in the case of a blue film.

x: The retardation in thickness direction value was confined to theseranges.

The results of above assessment are shown in the following Table 3.

3. Assessment of Patterning Properties

The patterning properties of each of color compositions shown in aboveTable 2 were evaluated as described below.

Namely, at first, by means of spin coating, each of the colorcompositions was coated on the surface of a glass substrate and thenprebaked at 70° C. for 15 minutes, thereby forming a coated film havinga film thickness of 2.3 μm. Then, by means of proximity exposure systemusing ultraviolet ray as an exposure light source, ultraviolet exposurewas performed through a photomask provided with a fine line pattern of50 μm. The dosage of exposure was set to eight levels, i.e. 30 J/cm², 40J/cm², 50 J/cm², 60 J/cm², 70 J/cm², 80 J/cm², 90 J/cm² and 100 J/cm².

Then, by making use of 1.25 wt % sodium carbonate, the coated film wasshower-developed and then washed. The resultant coated film was thensubjected to a heat treatment for 20 minutes at 230° C., thusaccomplishing the patterning of the coated film.

The film thickness of the filter segment thus obtained was divided bythe film thickness (2.3 μm) of the non-exposure/non-developing portion,thereby calculating the residual film ratio thereof. Then, an exposuresensitivity curve was plotted in a graph with the abscissa representingexposure dosages and the ordinate thereof representing residual filmratios after the development. Based on the exposure sensitivity curvethus obtained, the minimum quantity of exposure which enabled theresidual film ratio to keep 80% or more was defined as a saturatedexposure dosage. Then, based on the saturated exposure dosage, anappropriate quantity of exposure was determined. Then, each of colorlayers was irradiated with this appropriate quantity of exposure,thereby performing the assessment of patterning properties according tothe following standard.

∘: Developing velocity was appropriate and it was possible to form anormal pattern without peeling of pattern or failure of shape

Δ: Developing velocity was inclined to become slightly high or slow andthe peeling or shape failure was recognized partially in the pattern.

x: Developing velocity was not appropriate and peeling of pattern orfailure of shape was frequently recognized.

5. Assessment of Resistance to Chemicals

In the same manner as in the case of the above assessment of patterningproperties, a stripe pattern was formed on the surface of glasssubstrate and then the glass substrate was exposed to the followingconditions. Any change in external appearance of the pattern after thisexposure was observed by means of an optical microscope.

N-methyl-2-pyrolidone solvent: Immersed for 30 minutes (24° C.)

Isopropyl alcohol solvent: Immersed for 30 minutes (24° C.)

γ-butyrolactone solvent: Immersed for 30 minutes (24° C.)

The resistance to chemicals was performed according to the followingstandard.

∘: No change in external appearance under every conditions

x: Failures such as peeling of pattern, chips or cracks were recognized.

The aforementioned results are shown in the following Table 3.

TABLE 3 Phase Assessment Long- difference on patterning term inthickness property/ storage direction Rth developing Unit stability (nm)speed/adhesion Resistance Ex. 1 Color ∘ −5 ∘ ∘ ∘ compo- sition 1 Ex. 2Color ∘ −4 ∘ ∘ ∘ compo- sition 2 Ex. 3 Color ∘ 0 ∘ ∘ ∘ compo- sition 3Ex. 4 Color ∘ −2 ∘ ∘ ∘ compo- sition 4 Ex. 5 Color ∘ −3 ∘ ∘ ∘ compo-sition 5 Ex. 6 Color ∘ 1 ∘ ∘ ∘ compo- sition 6 Ex. 7 Color ∘ −4 ∘ ∘ ∘compo- sition 7 Ex. 8 Color ∘ −2 ∘ ∘ ∘ compo- sition 8 Comp. Color x 1 ∘x ∘ Ex. 1 compo- sition 9 Comp. Color x 4 x x Δ Ex. 2 compo- sition 10Comp. Color x 5 x Δ x Ex. 3 compo- sition 11 Comp. Color x −2 ∘ Δ Δ Ex.4 compo- sition 12 Comp. Color x 3 x x Δ Ex. 5 compo- sition 13 Comp.Color x 5 x x Δ Ex. 6 compo- sition 14 Comp. Color ∘ 8 x ∘ ∘ Ex. 7compo- sition 15 Comp. Color ∘ 6 x ∘ ∘ Ex. 8 compo- sition 16 Comp.Color ∘ 6 x ∘ ∘ Ex. 9 compo- sition 17

It will be recognized from the above Table 3 that the resin compositionsof Examples 1 to 8 wherein polymer compositions falling within the scopeof the present invention were employed were all excellent in everyrespects including not only the long-term storage stability, sensitivityand patterning properties of the photosensitive resin composition butalso the retardation in thickness direction and chemical resistance ofthe color layer to be obtained through the curing of the photosensitiveresin composition.

Whereas, in the case of the resin compositions of Comparative Examples 1to 9 wherein polymer compositions falling outside the scope of thepresent invention were employed, it will be recognized that at least anyone of the aforementioned features was found unsatisfactory.

Example 9 6. Manufacture of Color Filter

The color filters were manufactured through a combination of colorcompositions shown in above Table 3 and by making use of the methoddescribed below.

First of all, by means of spin coating, a color composition 8 formed ofa photosensitive red color composition was coated on the surface of aglass substrate having a black matrix formed thereon in advance and thenpre-baked for 20 minutes in a clean oven at a temperature of 70° C.Then, after being cooled to room temperature, the substrate was exposed,through a photomask, to ultraviolet rays by making use of an ultra-highpressure mercury lamp.

Thereafter, the resultant substrate was subjected to spray developmentby making use of an aqueous solution of sodium carbonate heated up to23° C., after which the resultant substrate was washed withion-exchanged water and air-dried. Further, the resultant substrate waspost-baked for 30 minutes in a clean oven at a temperature of 230° C.,thereby forming a red colored pixel having stripe-like configuration onthe substrate.

Then, by making use of a color composition 7 formed of a photosensitivegreen composition, a green pixel was formed in the same manner asdescribed above and, further, by making use of a color compositionformed of a photosensitive blue composition, the blue pixel was formedin the same manner as described above, thereby obtaining a color filter.The film thickness of each of these colored pixels was 2.0 μm in everycase.

7. Manufacture of a Liquid Crystal Display Device

An over-coat layer was formed on the surface of color filter obtained asdescribed above and then a polyimide alignment layer was formed thereon.Further, a polarizing plate was formed on the opposite surface of theglass substrate. On the other hand, a TFT array and pixel electrodeswere formed on one surface of another (second) glass substrate and apolarizing plate was formed on the opposite surface of this glasssubstrate.

A couple of glass substrates thus prepared were positioned face to faceso as to make the electrode layers thereof face to each other. Then,these glass substrates were aligned with each other while securing apredetermined gap between these substrates by making use of spacer beadsand then the outer circumference of this composite structure ofsubstrates was entirely sealed while leaving an opening for injecting aliquid crystal composition. Thereafter, a liquid crystal composition forVA was injected, via the opening, into the gap and then the opening wasclosed. The polarizing plate was furnished with an optical compensationlayer which was optimized so as to realize a wide viewing angle display.

The liquid crystal display device thus manufactured was assembled with aback light unit to obtain a liquid crystal panel of VA display mode.

Example 10, Comparative Examples 10 and 1

A color filter 2 was manufactured in the same manner as described inExample 9 except that a color composition 2 was employed as thephotosensitive blue composition. Then, by making use of this colorfilter 2, a liquid crystal panel of VA display mode was manufactured inthe same manner as described in Example 9 (Example 10).

Further, a color filter 3 was manufactured in the same manner asdescribed in Example 9 except that a color composition 14 was employedas the photosensitive red composition, a color composition 13 wasemployed as the photosensitive green composition and a color composition11 was employed as the photosensitive blue composition. Then, by makinguse of this color filter 3, a liquid crystal panel of VA display modewas manufactured in the same manner as described in Example 9(Comparative Example 10).

Further, a color filter 4 was manufactured in the same manner asdescribed in Example 9 except that a color composition 14 was employedas the photosensitive red composition, a color composition 13 wasemployed as the photosensitive green composition and a color composition9 was employed as the photosensitive blue composition. Then, by makinguse of this color filter 4, a liquid crystal panel of VA display modewas manufactured in the same manner as described in Example 9(Comparative Example 11).

8. Assessment of Visibility of Liquid Crystal Display Device onDisplaying Black Color

The liquid crystal display device manufactured as described above wasoperated so as to display black color and the quantity of the lightleaked out from the liquid crystal panel (orthogonally permeated light;leaked light) in the normal direction (approximately vertical direction)of liquid crystal panel and in a slanted direction which was inclined by45° from the normal direction (oblique angle) was visually observed.Further, the chromaticity as the panel was viewed in approximatelyvertical direction at the time of black display (u(⊥), v(⊥)) and thechromaticity as the panel was viewed obliquely by an angle of up to 60°in maximum from the normal direction (u(45), v(45)) were measured bymaking use of BM-5A (Topcon Co., Ltd.). Then, the color difference Δu′v′was calculated and the maximum value of Δu′v′ under the condition of0≦θ60° was determined. The ranking of assessment was as follows, theresults being illustrated in the following Table 4.

∘: Δu′v′≦0.05

x: Δu′v′>0.05

TABLE 4 Visibility Color filter Photosensitive composition usedassessment/ used Red Green Blue oblique staining Ex. 9 Color filter 1Color composition 8 Color composition 7 Color composition 1 ◯ Ex. 10Color filter 2 Color composition 8 Color composition 7 Color composition2 ◯ Comp. Ex. 10 Color filter 3 Color composition 14 Color composition13 Color composition 9 X Comp. Ex. 11 Color filter 4 Color composition14 Color composition 13 Color composition 11 X

It will be recognized from above Table 4 that since the liquid crystalpanels of Examples 9 and 10 were constructed in such a manner that theretardation in thickness direction values of red color pixels, greencolor pixels and blue color pixels fall within the range of +1 nm to −10nm, it was possible, through the application of the color filter thusobtained to a liquid crystal display device, to obtain a liquid crystaldisplay device which is excellent in oblique visibility.

Whereas, in the case of the liquid crystal panels of ComparativeExamples 10 and 11, since the red color pixels, green color pixels andblue color pixels of the color filter were created by making use ofcolor compositions which fall outside of the present invention, thebalance of retardation in thickness direction among the red pixel, thegreen pixel and blue pixel was poor, so that color shift was caused togenerate in the oblique direction, thus deteriorating the obliquevisibility thereof.

1. A color filter for a liquid crystal display device, comprising: aglass substrate; and a color layer formed on the substrate andconstituting color pixels of a plurality of colors, the color layerbeing formed through a curing of a color composition comprising at leastan acrylic resin, a coloring agent, and a resin exhibiting apermeability of not less than 80% in a total wavelength range of 400 to700 nm of visible light zone, the acrylic resin containing a copolymerformed of a first vinyl monomer having a benzyl group and a second vinylmonomer having a carboxyl group, the first vinyl monomer having afunction of regulating a retardation of a color layer and a content of76 to 91 mol % based on the solid matters of the acrylic resin, thecopolymer having a weight average molecular weight of 3000 to 11000 andan acid value of solid matter falling within the range of 30 to 85, andeach of color pixels exhibiting a retardation in thickness direction(Rth) falling within the range of 1 to −10 nm, Rth being a valuerepresented by a formula Rth={(Nx+Ny)/2−Nz}×d, wherein Nx is arefractive index in x-direction in a plane of a color layer, Ny is arefractive index in the y-direction in the plane of the color layer, Nzis a refractive index in a thickness direction of the color layer, x isdefined as a slow axis represented by Nx≧Ny, and d is a thickness (nm)of the color layer.
 2. The color filter according to claim 1, whereinthe first vinyl monomer is selected from the group consisting of benzylacrylate and benzyl methacrylate, and the second vinyl monomer isselected from the group consisting of acrylic acid, methacrylic acid,maleic acid, monoalkyl maleic acid, fumaric acid, monoalkyl fumaricacid, itaconic acid, monoalkyl itaconic acid, crotonic acid, maleicanhydride, itaconic anhydride and 2-methacryloyl propionic acid.
 3. Aliquid crystal display device which is provided with the color filterclaimed in claim 1.